During the holidays, I though about backupping. I wanted to have a simple backupping system that works automatically. That excluded RAID (too complicated) and DVD's (not automatic). Applications that seem to be useful in this regard include Simple Backup Suite and Unison. There is also a possibility to make a backup of the whole disc by using the dd command. However, my solution was to buy an USB disc and do some rsync+cron magic. Pretty much similarly as described in here.